The proposed research is concerned with the interaction of chemical carcinogens with DNA and the consequence (damage and repair) of this reaction as it relates to the integrity of the cell. Damage and repair of DNA in vivo will be monitored by an alkaline sucrose gradient method that uses a fluorometric determination of DNA in the gradient fractions. DNA damage and repair will be studied in euchromatin versus heterochromatin. The specificity of different carcinogens to induce damage and then the repair of damage will be compared in the chromatin fractions. The loss of specific alkylated products will be compared between euchromatin and heterochromatin.